Gas turbine fuel control

Abstract

An electronic fuel control for a gas turbine engine monitors the mass density of the fuel. As the mass density of the fuel varies when the fuel temperature changes or when the fuel type changes, the electronic fuel control adjusts an initial mass density to a corrected value based on the most recent measurement of mass fuel flow that was taken when the mass fuel flow measurement was known to be accurate. Accurately controlling mass fuel flow permits gas turbine engine designers to reduce tolerances in moving parts which improves the efficiency of the gas turbine engine.

I claim: 
     
       1. A fuel control for a gas turbine engine comprising: a) a metering valve having a variable flow area;   b) means for measuring said flow area of said metering valve which is adapted to produce a first signal directly related to said flow area;   c) means for measuring a mass flow of fuel through said metering valve which is adapted to produce a second signal directly related to said mass flow;   d) means for determining that said second signal conforms to a specified accuracy criteria which is adapted to produce a third signal that indicates that said second signal conforms to said accuracy criteria;   e) means for simultaneously storing said first and said second signals when said third signal indicates that said second signal conforms to said accuracy criteria;   f) means for producing a fourth signal that relates the quotient of said stored first signal and said stored second signal;   g) means for storing said fourth signal when said fourth signal is within a predetermined authority range;   h) means for producing a fifth signal that is equivalent to the product of said first signal and said stored fourth signal;   i) an electronic control that positions said metering valve as a function of said fifth signal.   
     
     
       2. A fuel control as described in claim 1 wherein said quotient is said stored second signal divided by said stored first signal.